Which number is the solution of n/3= -12? a: -36 b: -4 c: 4 d: 36

N/3= -12.
You want to get "N" by itself. On one side of the equation, with no other number. To do this, we do the opposite of what we have next to the letter "N"
In this case, N is being divided by 3, and the opposite of dividing is multiplying.
So you need to multiply both sides by 3.
The 3's on the left side cancel out, leaving N by itself.
Now you have N= -12 * 3
-12 * 3 = -36

So N = -36